CSV Deduplicator: Clean Your Data in One Click
Duplicate rows are a common problem in exported spreadsheets, CRM dumps, and database backups. This tool removes exact duplicates or deduplicates by a key column — keeping the first occurrence and showing you how many rows were eliminated.
All-Column vs Single-Column Deduplication
All-column mode treats a row as a duplicate only when every field matches exactly. Single-column mode (choose a key column like 'email' or 'id') keeps only the first row seen for each unique value in that column, even if other columns differ. Use all-column for exact full-row matches; use key-column when a single identifier should be unique.
First Occurrence Wins
When duplicates are found, the first occurrence in the file is kept and all subsequent duplicates are removed. This preserves the original row order and is deterministic — running the tool twice on the same file produces the same output.
Deduplication Stats
After processing, the tool shows three numbers: the original row count, the deduplicated row count, and the number of rows removed. This lets you quickly assess data quality — a large number of removed rows may indicate an upstream data issue worth investigating.
Practical Examples
Cleaning a CRM Contact Export
Remove duplicate contacts from a Salesforce or HubSpot CSV export.
- 1.Paste the exported CSV with a contact_id or email column
- 2.Select 'By key column' and choose 'email' from the dropdown
- 3.Review the stats showing how many duplicates were removed
- 4.Copy the deduplicated CSV for re-import
Two Deduplication Modes
- All-column: row is duplicate only if every field matches exactly
- Key-column: one unique value per selected column, first row wins
- Stats displayed: original count, kept count, removed count
- Header row always preserved and excluded from dedup logic
Good Use Cases
- Cleaning CRM exports before re-importing contact lists
- Removing duplicate log entries from aggregated CSV logs
- Deduplicating email lists to reduce bounce rates
- Normalizing merged CSVs from multiple data sources
Frequently Asked Questions
What does 'All columns' deduplication mean?
In all-columns mode, a row is considered a duplicate only if every field matches another row exactly. Two rows that share an email but differ in any other column are kept as separate rows.
What does deduplication by a specific column mean?
When you select a column (e.g. 'email'), the first row for each unique value in that column is kept and all subsequent rows with the same value are removed — even if other columns differ.
Is the first or last occurrence kept?
The first occurrence is always kept. All later duplicates are discarded.
Is my data sent to a server?
No. All processing happens in your browser. Your CSV data never leaves your device.